U.S. law passed in June 1917 because of fears of German spies and saboteurs. It resulted in thousands of arrests and convictions, but not one was for active spying; most were for dissent.
The first person to be charged for espionage under the law was Daniel Ellsberg, who leaked the Pentagon Papers to the press and Congress in 1971. However, efforts by President Nixon's staff to build a case against Ellsberg -- including breaking into his psychiatrist's office -- led to the charges being dismissed before he was brought to trial.
The second American to be charged under the espionage act was Samuel L. Morison.
